1. Field of Invention
The invention relates to a power circuit supplying power to an electronic device and, more particularly, to a power circuit with a self-protection function.
2. Related Art
A switch power circuit has characters of low loss, high switching frequency and stable operation. Thus, it is widely used in a liquid crystal display (LCD) television, a computer system, a handheld device and other electronic devices.
FIG. 1 is a schematic diagram showing architecture of a conventional power circuit.
The power circuit 10 receives input signals and outputs signals. The power circuit 10 includes a logic control circuit 2 and a driver circuit 3.
After the logic control circuit 2 receives the input signals, it converts the input signals to multiple output signals and sends them to the driver circuit 3, respectively. The input signals include an enable (EN) signal and a pulse width modulation (PWM) signal. The EN signal controls operation of the power circuit, and the PWM signal provides motion commands to the power circuit.
When the driver circuit 3 receives the multiple output signals, it outputs a drive signal to a switch circuit (not shown). The driver circuit 3 includes a first driver amplifier 31 and a second driver amplifier 32. The first driver amplifier 31 and the second driver amplifier 32 receive different output signals and output a first gate (UGATE) drive signal and a second gate (LGATE) drive signal, respectively.
The switch circuit connected to the power circuit 10 usually includes a first metal-oxide-semiconductor field-effect transistor (MOSFET) and a second MOSFET for receiving the first gate (UGATE) drive signal and the second gate (LGATE) drive signal LGATE, respectively.
The power circuit 10 and the switch circuit may be called the switch power circuit. When the switch power circuit is used in client, the components inside are easy to be burned out due to bad environment or operation errors. If the switch power circuit does not have a self-protection function, when a certain component, such as the first driver amplifier 31, the second driver amplifier 32, the first MOSFET or the second MOSFET, is burned out, other relating components may be also burned out due to a chain reaction. For example, when the first MOSFET is burned out, the connected first driver amplifier 31 is also burned out, or when the first driver amplifier 31 is abnormal, the first MOSFET may also be burned out.